1. Field of the Invention
The invention relates to an endoscopic grasping tool which is used for grasping and recovering a foreign material or the like in a body cavity, with being passed through a treatment tool insertion channel of an endoscope.
The endoscopic grasping tool is roughly classified into two categories, i.e., a tool in which a link mechanism is disposed at a tip end of a sheath to be passed through a treatment tool insertion channel and grasping pieces are opened and closed by the link mechanism, and that in which grasping pieces that are elastically deformable are protruded from and retracted into a tip end of a sheath and, when the grasping pieces are protruded, they are expanded by their own elasticity. The grasping tool of the invention belongs to the former category.
2. Description of the Related Art
In an endoscopic grasping tool wherein grasping pieces are opened and closed by a link mechanism disposed at a tip end of a sheath which is to be passed through a treatment tool insertion channel of an endoscope, usually, the grasping pieces are formed by a pair of beak-like members and a foreign material or the like is grasped and recovered by being nipped between the beak-like grasping pieces.
In the case where a foreign material such as a bean entering a bronchial tube is to be recovered, for example, the foreign material which is nipped between the pair of grasping pieces may be broken by a grasping force. When such a foreign material is once broken, it is very difficult to recover the foreign material.
An endoscopic grasping tool is remotely operated from an operator-side end of a long sheath which is passed through a treatment tool insertion channel. Therefore, a feeling of hardness and the like of a foreign material are hardly transmitted to the hand of the operator.
The operator tends to exert a strong force in order to prevent a foreign material from dropping or to surely grasp the foreign material. In the case where a fragile foreign material or the like such as a bean is to be recovered, therefore, the above-mentioned trouble is liable to occur.
By the way, in an endoscopic grasping tool of a type wherein a grasping piece which is elastically deformable is protruded from or retracted into the tip end of a sheath and which, when protruded, is expanded by its elasticity, the grasping piece is moved in a direction of the retraction into the sheath when a foreign material or the like is grasped. Consequently, a foreign material or the like often fails to be grasped.
Furthermore, in an endoscopic grasping tool of this type, when a foreign material or the like is grasped, the portion of the grasping piece which is outside the sheath becomes very short and hence the grasping piece cannot be elastically deformed to a large degree. This may produce a state where a large grasping force is applied to the foreign material and the foreign material crushes.